Chemical Precipitation of BaSn(OH)6 and Its Thermal Destruction in the Process of BaSnO3 Preparation

The synthesis of barium hexahydroxostannate BaSn(OH)6 and its thermal destruction leading to the barium stannate BaSnO3 have been studied. It is shown that the most intensive decomposition of BaSn(OH)6 occurs in the temperature range of 200–650°C. Crystallization of BaSnO3 proceeds in a narrow temperature range (650–675°C), and the maximum of the corresponding exo-effect is located at 667°C. It was found that at 500°C (within 60 min) BaSn(OH)6 completely decomposes with the formation of X-ray amorphous powder. When the material is kept at 600°C (60 min), crystallization of barium stannate BaSnO3 with perovskite structure takes place. The crystalline impurity of barium carbonate contained in the semiproduct is preserved up to 600°C, and at temperatures from 700°C the single-phase BaSnO3 is formed. The crystallization temperature of barium stannate can be reduced by 50–75°C due to thermal exposure of the powder for 40–60 min. Holding the semiproduct at 600°C for 60 min forms barium stannate with an average crystallite size of 21 ± 2 nm, and at 700°C there is a slight increase in this parameter (up to 22 ± 2 nm). With increasing temperature up to 1000°C there is intensification of crystallite enlargement process (up to 34 ± 3 nm). The obtained BaSnO3 powder, according to scanning electron microscopy data, consists of microrods (average length is about 85 μm; average diameter is about 10 μm). The surface of the rods is partially covered with spherical particles formed from smaller primary particles of about 30 nm in size.